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From:   Thomas Gleixner <tglx@linutronix.de>
To:     "liaochang \(A\)" <liaochang1@huawei.com>,
        xuyihang <xuyihang@huawei.com>, Ming Lei <ming.lei@redhat.com>
Cc:     Peter Xu <peterx@redhat.com>, Christoph Hellwig <hch@lst.de>,
        Jason Wang <jasowang@redhat.com>,
        Luiz Capitulino <lcapitulino@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Michael S. Tsirkin" <mst@redhat.com>, minlei@redhat.com
Subject: Re: Virtio-scsi multiqueue irq affinity
In-Reply-To: <9903df53-8a84-fe89-7ae0-aac8e6d3f42f@huawei.com>
References: <20190318062150.GC6654@xz-x1> <alpine.DEB.2.21.1903231805310.1798@nanos.tec.linutronix.de> <20190325050213.GH9149@xz-x1> <20190325070616.GA9642@ming.t460p> <alpine.DEB.2.21.1903250948490.1798@nanos.tec.linutronix.de> <20190325095011.GA23225@ming.t460p> <0f6c8a5f-ad33-1199-f313-53fe9187a672@huawei.com> <87zgx5l8ck.ffs@nanos.tec.linutronix.de> <9903df53-8a84-fe89-7ae0-aac8e6d3f42f@huawei.com>
Date:   Mon, 10 May 2021 09:54:58 +0200
Message-ID: <87r1ifkoq5.ffs@nanos.tec.linutronix.de>
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Liao,

On Mon, May 10 2021 at 11:19, liaochang wrote:
> 1.We have a machine with 36 CPUs,and assign several RT threads to last
> two CPUs(CPU-34, CPU-35).

Which kind of machine? x86?

> 2.I/O device driver create single managed irq, the affinity of which
> includes CPU-34 and CPU-35.

If that driver creates only a single managed interrupt, then the
possible affinity of that interrupt spawns CPUs 0 - 35.

That's expected, but what is the effective affinity of that interrupt?

# cat /proc/irq/$N/effective_affinity

Also please provide the full output of

# cat /proc/interrupts

and point out which device we are talking about.

Thanks,

        tglx